The present invention relates generally to the control of coccidiosis and, more specifically, to the application of plant parts, plant extracts and compounds to control coccidiosis in poultry and other animals.
Coccidiosis is a major disease in the poultry industry and according to a recent survey, it is estimated that the global impact is greater than $3 billion USD annually (worldpoultry.net/Broilers/Health/2009/9/In-ovo-vaccination-against-coccidiosis-WP006949W/—accessed Jun. 18, 2013). Coccidiosis is caused by a protozoan parasite, namely Eimeria, belonging to the phylum Apicomplexa, and the family Eimeriidae (Clare, R. A and Danforth, H. D (1989). Major histocompatibility complex control of immunity elicited by genetically engineered Eimeria tenella (Apicomplexa) antigen in chickens. Infection and immunity, 57 (3): 701-705). The parasite invades the gut cells and causes necrosis in the intestine which leads to malabsorption, diarrhea, morbidity, reduction of weight gain, poor feed conversion, and, in severe cases, mortality (Williams, R. B (2005). Intercurrent coccidiosis and necrotic enteritis of chickens: Rational, integrated disease management by maintenance of gut integrity. Avian Pathology, 34(3), 159-180). Seven different species of Eimeria, E. acervulina, E. brunetti, E. maxima, E. mitis, E. necatrix, E. praecox, and E. tenella are known to cause coccidiosis in poultry (Williams, 2005) and the species are highly host and site specific. E. tenella is one of the major species causing coccidiosis in poultry, and their site of infection is the caecum (Khazandi, M and Tivey, D (2010). Developing an in vitro method for Eimeria tenella attachment to its preferred and non-preferred intestinal sites. Experimental Parasitology, 125 (2), 137-140). Coccidiosis is currently controlled by medication, but the increasing emergence of drug-resistant strains of Eimeria requires the development of an alternative control strategy. Since plants are known to possess antiparasitic and anticoccidial activity due to the presence of phenolic compounds (Tipu, M. A., Akhtar, M. S., Anjum, M. I and Raja, M. L (2006). New dimension of medicinal plants as animal feed. Pakistan vet. J., 26(3): 144-148), they could be potential sources of bioactive molecules against coccidiosis in poultry.
Others have attempted to use plant parts or plant extracts in treating coccidiosis. For example, McCann et al. tested the effect of Sweet Chestnut Wood tannins on the performance of broiler chicks vaccinated with a live coccidia vaccine (M. E. E. McCann, E. Newell, C. Preston and K. Forbes. The Use of Mannan-Oligosaccharides and/or Tannin in Broiler Diets. Intl. J. of Poultry Sci. 5 (9): 873-879, 2006). They reported that supplementation with mannan-oligosaccharides or tannins, either individually or in combination, did not reduce the impact of the coccidiosis.
Wang et al. teach the use of a grape seed proanthocyanidin extract on coccidiosis (Wang, et al. Influence of Grape Seed Proanthocyanidin Extract in Broiler Chickens: Effect on Chicken Coccidiosis and Antioxidant Status. Poultry Science. 87:2273-2280, 2008). They attributed activity to the anti-inflammatory and antioxidant properties of the proanthocyanidins, a condensed tannin rather than a hydrolysable tannin.
Naidoo et al. teach an in vivo study using four plants selected based on their antioxidant activity (Naidoo et al. The value of plant extracts with antioxidant activity in attenuating coccidiosis in broiler chickens. Veterinary Parasitology. 153:214-219; 2008). They observed that one of the plants (Tulbaghia violacea) reduced the Eimeria oocyst counts in the chicken excreta and they speculate that this effect could be due to the antioxidant compound S (methylthiomethyl) cysteine sulfoxide.
McDougald et al. describe the use of a muscadine pomace to enhance resistance to coccidiosis in broiler chickens (McDougald et al. Enhancement of Resistance to Coccidiosis and Necrotic Enteritis in Broiler Chickens by Dietary Muscadine Pomace. Avian Diseases. 52: 646-651; 2008). Muscadine pomace is a by-product of grapes used in wine production. They make no mention of efficacy of any specific compounds in the pomace. The proposed anti-coccidial activity differs significantly from the activities proposed by Wang et al. and Naidoo et al.